Rolling Membrane Stent Delivery Reducing Friction Binding
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Solution Overview
Problem
Catheter delivery systems face challenges with friction forces when deploying self-expanding stents, particularly with longer stents and smaller diameters, which can lead to premature release or binding issues due to friction between the sheath and stent, and the use of lubricants is undesirable for consistency and reliability.
Innovation Solution
A rolling membrane system with a slitter that progressively slits the inner sleeve during stent release, allowing the outer sleeve to slide over the abluminal surface of the inner sleeve, reducing friction and preventing premature release, and the outer sleeve is designed with radial slits to accommodate diameter variations and reduce binding risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional single-layer sheath is used to deliver self-expanding stents, then the structure is simple, but friction forces between the sheath and stent increase with stent length, causing binding and premature release issues
Solution Approach 1:
The sheath is divided into an inner sleeve and an outer sleeve that can move relative to each other. The inner sleeve radially constrains the stent while the outer sleeve provides additional protection. This segmentation allows the inner sleeve to be pulled back independently to release the stent, reducing friction-related binding issues while maintaining structural simplicity.
2Length of moving object
If the stent length is increased to treat longer stenotic lesions, then more extensive coverage is achieved, but friction forces between the sheath and stent increase, leading to binding and deployment failures
Solution Approach 1:
By segmenting the sheath into movable inner and outer sleeves, the system can accommodate longer stents without proportional increases in friction-related problems. The inner sleeve's independent retraction capability ensures reliable stent release even with extended stent lengths.
Solution Approach 2:
A lubricant layer is introduced as an intermediary between the inner and outer sleeves to reduce friction forces. This lubricant layer enables smooth relative movement of the sleeves during stent deployment, preventing binding issues that would otherwise occur with longer stents.
3Volume of moving object
If the passing diameter of the delivery system is reduced to access smaller vessels, then vascular access is improved, but the outer sleeve must slide over the inner sleeve with higher friction, causing binding
Solution Approach 1:
A lubricant layer is applied between the inner and outer sleeves to reduce friction during their relative movement. This intermediary lubricant layer enables smooth sliding of the outer sleeve over the inner sleeve even in the constrained space of reduced-diameter delivery systems, preventing binding and ensuring reliable stent deployment.
4Ease of operation
If lubricant is applied between the inner and outer sleeves to reduce friction, then sleeve sliding is improved, but the use of extraneous substances at the distal end is increased, affecting consistency and reliability
Solution Approach 1:
The system uses a disposable lubricant coating applied to the inner sleeve surface. This thin, single-use lubricant layer provides sufficient friction reduction for the duration of the procedure and is discarded with the catheter system afterward, eliminating concerns about residual lubricant affecting subsequent procedures while maintaining deployment consistency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution ensures smooth and reliable stent deployment by minimizing friction and preventing binding, allowing for the successful release of longer stents with greater radial force, while maintaining system integrity and reducing the risk of component failure.
Implementation Method 1
friction forces between the stent and the surrounding sheath must be taken into account when devising a delivery system that will allow the sheath to slide proximally over the full length of the outwardly-pushing, self-expanding stent
Implementation Method 2
adopt a 'rolling membrane' sheath system, in which the sheath is at least double the length of the stent that it surrounds, being doubled back on itself at a point distally beyond the distal end of the stent. Then, proximal withdrawal of the radially outer doubled back portion of the sheath length will cause the 'rolling edge' between the outer and inner sheath portions to retreat proximally, rolling proximally down the length of the stent
Implementation Method 3
It has been proposed to provide a lubricant between the inner and outer radial portions of a rolling membrane release system
Data Source
AI summary
A delivery device for a self-expanding implant, including an inner shaft, a slidable member disposed over the inner shaft, an actuation member, a rolling membrane, and a slitting member. The actuation member is coupled to the slidable member, and the rolling membrane is disposed over the self-expanding implant, the rolling member including a proximal end secured to the inner shaft, and a distal end secured to the slidable member. The slitting member includes a proximal end secured to the inner shaft, and a distal end secured to the slidable member, such that translation of the slidable member over the inner shaft in a proximal direction contemporaneously translates the rolling membrane and the slitting member in the proximal direction.